Patent Document 1 discloses that a compound such as lurasidone can be orally administered and an oral preparation can be prepared by blending an active ingredient with a conventional carrier, excipient, binder, stabilizer and the like, but there is no disclosure of an oral preparation which shows a rapid dissolution and has an equivalent dissolution profile of the active ingredient even though contents of the active ingredient therein are varied in the wide range, particularly an oral preparation with increased contents of the active ingredient which has a similar dissolution profile to that of multiple tablets with a lower content of the active ingredient per tablet.
For the purpose of securing the bioequivalence when pharmaceutical preparations with different contents of the active ingredient were administered so as to be the same dose to each other, a guideline has been issued, i.e., “Guideline for Bioequivalence Studies of Oral Solid Dosage Forms with Different Content” (Notification No. 64 of the Evaluation and Licensing Division, Pharmaceutical and Food Safety Bureau, promulgated on Feb. 14, 2000) by which it has been required that pharmaceutical preparations with different contents should have an equivalent dissolution profile in each test solution such as buffers of pH 1.2, 3.0 to 5.0 and 6.8 (which correspond to the pH values of stomach, intestine and oral cavity, respectively), water, and saline.
Patent Document 2 discloses an oral preparation comprising lurasidone as an active ingredient, which shows a rapid dissolution and has an equivalent dissolution profile even though contents of the active ingredient therein are varied, particularly an oral preparation with increased contents of the active ingredient which has an equivalent dissolution profile to that of multiple tablets with a lower content of the active ingredient per tablet and can release a slightly water-soluble active ingredient therefrom at a desired concentration.
Patent Document 2 further discloses an oral preparation, particularly a tablet, which shows a rapid dissolution of the active ingredient even though contents of the active ingredient therein are varied in the range of several mg to several tens of mg (e.g. in the range of 5 mg to 20 mg or in the range of 5 mg to 40 mg), and further has an equivalent dissolution profile in the same componential ratio. An oral preparation has been frequently required to be a preparation with higher contents of the active ingredient in order to get higher clinical effects, or a preparation which has an equivalent dissolution profile to that of multiple tablets and can release the active ingredient therefrom at a desired concentration in wider ranges of contents in order to adjust clinical effects depending on conditions of patients. The art disclosed in Patent Document 2 may provide an oral preparation which has an equivalent dissolution profile in the range of 5 mg to 40 mg of lurasidone per tablet, as shown in FIG. 1. However, as shown in FIG. 2, when the content of the active ingredient per tablet was increased to double, i.e., 80 mg tablet, it could not have an equivalent dissolution profile. Hence, it remains in a state of administering multiple tablets at one time or using a tablet having a big size which is difficult to administer. Therefore, for such a slightly water-soluble active ingredient as lurasidone, it has been difficult to provide an oral preparation having an equivalent dissolution profile even in high content or in wider ranges of contents of the active ingredient.
In Patent Document 2, a water-soluble polymer binder includes starch, but there is no description about a pregelatinized starch therein. The pregelatinized starch is known to remarkably improve a disintegration and a dissolution of a pharmaceutical composition as described, for example, in Patent Document 3, but it is often used, typically, in 10% or less of contents as also described in Non-patent Document 1.    Patent Document 1: JP2800953    Patent Document 2: WO2002/024166    Patent Document 3: JP2000-26292    Non-patent Document 1: Handbook of Pharmaceutical Excipients, 2nd edition, 491, 1994, The Pharmaceutical Press